Curvaton Decay by Resonant Production of the Standard Model Higgs

TL;DR

This paper demonstrates that a curvaton coupled to the Standard Model Higgs can have its decay delayed until electroweak symmetry breaking due to thermal effects, allowing it to generate the observed curvature perturbation.

Contribution

It provides analytical models showing delayed curvaton decay via resonant Higgs production, even with large couplings, and extends to other species coupled to thermal backgrounds.

Findings

Resonant decay can be delayed until electroweak scale.

Large couplings (~0.1) still produce the correct curvature perturbation.

Analytical expressions for delay time and decay width are derived.

Abstract

We investigate in detail a model where the curvaton is coupled to the Standard Model higgs. Parametric resonance might be expected to cause a fast decay of the curvaton, so that it would not have time to build up the curvature perturbation. However, we show that this is not the case, and that the resonant decay of the curvaton may be delayed even down to electroweak symmetry breaking. This delay is due to the coupling of the higgs to the thermal background, which is formed by the Standard Model degrees of freedom created from the inflaton decay. We establish the occurrence of the delay by considering the curvaton evolution and the structure of the higgs resonances. We then provide analytical expressions for the delay time, and for the subsequent resonant production of the higgs, which ultimately leads to the curvaton effective decay width. Contrary to expectations, it is possible to obtain the observed curvature perturbation for values of the curvaton-higgs coupling as large as 0.1. Our calculations also apply in the general case of curvaton decay into any non Standard Model species coupled to the thermal background.